Packages, generally of the single-use type, for small doses of products are known which are constituted by a tray made of plastics or metallic material that is closed by a heat-sealable film after filling.
Various methods for obtaining these packages are known.
In particular, it is known to fill and close the trays while they are fed with a substantially horizontal arrangement and so that their cavities are directed upward.
According to a first known working method, the packages are obtained by feeding the trays along an advancement direction, along which they encounter a unit for dosing the product and a subsequent unit for applying the covering film, both units being fixed with respect to the advancement direction.
Therefore, the feeding of the trays is discontinuous and provides appropriate stationary periods at said units.
However, this packaging method is not free from drawbacks, including the fact that the repeated accelerations and decelerations to which the trays are subjected cause an agitation of the product introduced therein that increases as its viscosity decreases.
Certain refinements are known in order to avoid accidental escape of the product during transfer from the dosage unit to the film application unit.
A first known refinement consists in dosing the amount of product that is introduced in each tray so as to occupy its useful volume only partially.
The percentage of useful volume that is occupied by the product is on the order of 75% and must decrease as the ratio between the extension of the base and the depth of the cavity of the trays being used increases.
By proceeding in this way, however, one obtains packages that have some drawbacks, linked in particular to consumer appreciation.
Partial filling of the packages is in fact usually ascribed to accidental products leaks.
Moreover, the fact of using packages that are “oversized” with respect to the amount of product contained therein is sometimes deemed misleading, in that it is aimed at fooling consumers regarding the content of said packages.
As an alternative, it is possible to reduce the rate at which the trays are fed from the dosage unit to the film application unit, penalizing however the productivity and low cost of the manufacturing cycle.
In order to obviate these drawbacks, a second operating method is also known which allows to reduce the agitation of the product introduced in the tray during travel toward the film application unit.
In this case, the packages are obtained by feeding the trays along an advancement direction, along which they encounter a so-called “chaser” product dosage unit, which can move alternately along said direction, and a subsequent film application unit that is fixed with respect to said direction.
The filling unit performs a translational motion for a certain extent together with the trays during filling; directly upstream of the film application unit, filling is completed; then the dosage unit returns to its initial configuration while the filled tray continues to advance until it reaches the application unit.
However, even this operating method does not allow to achieve optimum filling of the resulting packages.
In order to further reduce the agitation of the product in the trays, it is known to increase the viscosity of said product by introducing appropriate amounts of thickening additives.
However, these additives can alter the characteristics of the product and may form deposits that remain on the bottom of the package after the product contained therein has been used up, and a perception of poor quality or deterioration of said product is sometimes associated with said deposits.